Therapeutic immune modulation by stem cell secreted exosomes

ABSTRACT

Disclosed are methods, compositions of matter, and protocols useful for the induction of a therapeutic immune modulatory response through administration of exosomes derived from a stem cell source. In one embodiment, said stem cell source is endometrial regenerative cells. Specifically, in one embodiment stem cell derived exosomes are used as a method of treating an autoimmune condition such as rheumatoid arthritis, multiple sclerosis, or systemic lupus erythromatosis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 to U.S.Provisional Application Ser. No. 61/592,636 filed Jan. 31, 2012, theentirety of which is hereby incorporated by reference.

FIELD OF THE INVENTION

The invention pertains to the field of immune modulation, specifically,the invention relates to immune modulation via administration ofmicrovesicular particles derived from cells with regenerative potentialsuch as stem cells. More specifically, the invention pertains toinhibition of autoimmunity, transplant rejection, inflammation, andgraft versus host disease through administration of exosomes.

BACKGROUND OF THE INVENTION

Exosomes are nano-size particles between 40-100 nm in size originallyidentified as a byproduct of reticulocyte maturation. Exosomes have beendescribed from numerous cell types including tumors, platelets, andimmune cells such as dendritic cells. The role of exosomes in immunemodulation has been historically restricted to the area of dendriticcell exosomes, which are known to carry MHC molecules, antigens, andboth costimulatory and co-inhibitory molecules. The majority of work inthe area of exosome immune modulation has focused on stimulation ofimmunity, particularly in the area of cancer, in which exosome-basedvaccines have been developed and entered clinical trials.

Very recently, exosomes have been identified in conditioned media ofvarious stem cell populations including mesenchymal stem cells, and CD34cells. These exosomes have been studied as “trophic factors” andstimulators of angiogenesis.

However to date, the use of exosomes derived from stem cells for immunemodulation has not been performed. Mesenchymal stem cells possessadvantages to DC or other immune cells in that they can be generated inlarge quantities, that their membrane products have an affinity towardsthe draining lymph node, and that they possess other known regenerativeactivities.

It is the scope of the current invention to overcome limitations ofDC-exosome based immune modulation through the use of MSC.

SUMMARY OF THE INVENTION

The current invention provides methods of inducing immune modulation ina mammal through administration of exosomes derived from stem cellpopulations. In one aspect of the invention, exosomes are derived frombone marrow mesenchymal stem cells. In another aspect, exosomes areisolated from culture of endometrial regenerative cells (ERC). Exosomesmay be used to induce specific or non-specific tolerance. In oneembodiment, exosomes are used to facilitate acceptance of an organ ortissue. In another embodiment, exosomes are derived from ERC that areused for therapeutic use and exosomes from the same donor areadministered along with ERC for treatment of an individual in need oftreatment.

Further methods include neuronal stem cells selected based on expressionof one or more of the following antigens: RC-2, 3CB2, BLB, Sox-2hh,GLAST, Pax 6, nestin, Muashi-1, NCAM, A2B5 and prominin. Further methodsinclude circulating peripheral blood stem cells characterized by abilityto proliferate in vitro for a period of over 3 months. Further methodsinclude circulating peripheral blood stem cells characterized byexpression of CD34, CXCR4, CD117, CD113, and c-met. Further methodsinclude circulating peripheral blood stem cells that lack substantialexpression of differentiation associated markers. Further methodsinclude differentiation associated markers selected from a groupcomprising of CD2, CD3, CD4, CD11, CD11 a, Mac-1, CD14, CD16, CD19,CD24, CD33, CD36, CD38, CD45, CD56, CD64, CD68, CD86, CD66b, and HLA-DR.

Further embodiments encompass methods wherein mesenchymal stem cellsexpress one or more of the following markers: STRO-1, CD105, CD54,CD106, HLA-I markers, vimentin, ASMA, collagen-1, fibronectin, LFA-3,ICAM-1, PECAM-1, P-selectin, L-selectin, CD49b/CD29, CD49c/CD29,CD49d/CD29, CD61, CD18, CD29, thrombomodulin, telomerase, CD10, CD13,STRO-2, VCAM-1, CD146, and THY-1. Further embodiments encompass methodswherein mesenchymal stem cells do not express substantial levels ofHLA-DR, CD117, and CD45. Further embodiments encompass methods whereinmesenchymal stem cells are derived from a group selected from: bonemarrow, adipose tissue, umbilical cord blood, placental tissue,peripheral blood mononuclear cells, differentiated embryonic stem cells,and differentiated progenitor cells. Further embodiments encompassmethods wherein germinal stem cells express markers selected from agroup comprising of Oct4, Nanog, Dppa5 Rbm, cyclin A2, Tex18, Stra8,Dazl, beta 1- and alpha6-integrins, Vasa, Fragilis, Nobox, c-Kit, Sca-1and Rex1. Further embodiments encompass methods wherein adipose tissuederived stem cells express markers selected from a group consisting of:CD13, CD29, CD44, CD63, CD73, CD90, CD166, Aldehyde dehydrogenase(ALDH), and ABCG2. Further embodiments encompass methods wherein adiposetissue derived stem cells are a population of purified mononuclear cellsextracted from adipose tissue capable of proliferating in culture formore than 1 month. Further embodiments encompass methods whereinexfoliated teeth derived stem cells express markers selected from thegroup consisting of: STRO-1, CD146 (MUC18), alkaline phosphatase, MEPE,and bFGF.

Further embodiments encompass methods wherein hair follicle stem cellsexpress markers selected from a group comprising of: cytokeratin 15,Nanog, and Oct-4. Further embodiments encompass methods wherein hairfollicle stem cells are capable of proliferating in culture for a periodof at least one month. Further embodiments encompass methods whereinhair follicle stem cells secrete one or more of the following proteinswhen grown in culture: basic fibroblast growth factor (bFGF),endothelin-1 (ET-1) and stem cell factor (SCF).

Further embodiments encompass methods wherein dermal stem cells expressmarkers selected from a group comprising of: CD44, CD13, CD29, CD90, andCD105. Further embodiments encompass methods wherein dermal stem cellsare capable of proliferating in culture for a period of at least onemonth. Further embodiments encompass methods wherein parthenogenicallyderived stem cells are generated by addition of a calcium flux inducingagent to activate an oocyte followed by enrichment of cells expressingmarkers selected from a group comprising of SSEA-4, TRA 1-60 and TRA1-81.

Further embodiments encompass methods wherein reprogrammed stem cellsare selected from a group comprising of: cells subsequent to a nucleartransfer, cells subsequent to a cytoplasmic transfer, cells treated witha DNA methyltransferase inhibitor, cells treated with a histonedeacetylase inhibitor, cells treated with a GSK-3 inhibitor, cellsinduced to dedifferentiate by alteration of extracellular conditions,and cells treated with various combination of the mentioned treatmentconditions. Further embodiments encompass methods wherein nucleartransfer comprises introducing nuclear material to a cell substantiallyenucleated, said nuclear material deriving from a host whose geneticprofile is sought to be dedifferentiated.

Further embodiments encompass methods wherein cytoplasmic transfercomprises introducing cytoplasm of a cell with a dedifferentiatedphenotype into a cell with a differentiated phenotype, such that saidcell with a differentiated phenotype substantially reverts to adedifferentiated phenotype. Further embodiments encompass methodswherein DNA demethylating agent is selected from a group comprising of:5- azacytidine, psammaplin A, and zebularine. Further embodimentsencompass methods wherein histone deacetylase inhibitor is selected froma group comprising of: valproic acid, trichostatin-A, trapoxin A anddepsipeptide. Further embodiments encompass methods wherein cells areidentified based on expression multidrug resistance transport protein(ABCG2) or ability to efflux intracellular dyes such as rhodamine-123and or Hoechst 33342. Further embodiments encompass methods whereincells are derived from tissues such as pancreatic tissue, liver tissue,smooth muscle tissue, striated muscle tissue, cardiac muscle tissue,bone tissue, bone marrow tissue, bone spongy tissue, cartilage tissue,liver tissue, pancreas tissue, pancreatic ductal tissue, spleen tissue,thymus tissue, Peyer's patch tissue, lymph nodes tissue, thyroid tissue,epidermis tissue, dermis tissue, subcutaneous tissue, heart tissue, lungtissue, vascular tissue, endothelial tissue, blood cells, bladdertissue, kidney tissue, digestive tract tissue, esophagus tissue, stomachtissue, small intestine tissue, large intestine tissue, adipose tissue,uterus tissue, eye tissue, lung tissue, testicular tissue, ovariantissue, prostate tissue, connective tissue, endocrine tissue, andmesentery tissue.

Further embodiments encompass methods wherein committed progenitor cellsare selected from a group comprising of: endothelial progenitor cells,neuronal progenitor cells, and hematopoietic progenitor cells. Furtherembodiments encompass methods wherein committed endothelial progenitorcells are purified from the bone marrow. Further embodiments encompassmethods wherein committed endothelial progenitor cells are purified fromperipheral blood. Further embodiments encompass methods whereincommitted endothelial progenitor cells are purified from peripheralblood of a patient whose committed endothelial progenitor cells aremobilized by administration of a mobilizing agent or therapy. Furtherembodiments encompass methods wherein stem cells are cultured in athree-dimensional bioreactor. Further embodiments encompass methodswherein stem cells are induced to produce an increased amount ofexosomes. Further embodiments encompass methods wherein induction ofexosomes from said stem cells is achieved by treatment of said stemcells with cytokines. Further embodiments encompass methods whereinexosomes are concentrated by a means selected from: a)ultracentrifugation; b) column chromatography; c) size exclusion; d)filtration through a device containing an affinity matrix selectivetowards exosomes. Further embodiments encompass methods wherein exosomesgenerated from said stem cells are used to inhibit inflammation in aninjured tissue. Further embodiments encompass methods wherein exosomesare transfected with a genetic material so as to allow delivery of saidgenetic material to an immune cell. Further embodiments include methodsof treating an autoimmune condition through administration of apopulation of stem cell exosomes capable of suppressing a biologicalpathway associated with an immune pathway associated with saidautoimmune condition.

Further embodiments encompass methods wherein an autoimmune condition isselected from a group comprising of: a) diabetes; b) multiple sclerosis;c) rheumatoid arthritis; d) Hashimoto's thyroiditis; e) graft rejection;and f) graft versus host disease. Further embodiments include methods oftreating an autoimmune condition comprising incorporating one or moreautoantigens into said exosomes generated from said stem cells, withincorporation of said autoantigen being accomplished by introductioninto said stem cell or introduction into said exosome generated by saidstem cell and administering said exosomes into a patient in needthereof. Further embodiments encompass methods of treating an autoimmunecondition in a mammal comprising administering exosomes derived fromstem cells that have been transfected one or more autoantigensrepresenting said autoimmune condition. Further embodiments encompassmethods wherein exosomes are derived from embryonic stem cells. Furtherembodiments encompass methods wherein exosomes are derived frommesenchymal stem cells.

Further embodiments encompass methods of treating an autoimmunecondition comprising of: a) obtaining a mesenchymal stem cell; b)introducing into said mesenchymal stem cell an antigen, in a manner suchthat said antigen is introduced into said mesenchymal stem cell in amanner so that said antigen is incorporated by said mesenchymal stemcell such that said antigen enters the exosomes that are released bysaid mesenchymal stem cell; c) purifying said antigen bearing exosomes;and d) administering said antigen-expressing exosomes into a patient inneed of therapy. Further embodiments encompass methods wherein amesenchymal stem cell is selected from a group of mesenchymal stem cellsselected from a group comprising of a) a bone marrow mesenchymal stemcell; b) an adipose derived mesenchymal stem cell; c) a dental pulpderived mesenchymal stem cell; d) a fallopian tube derived mesenchymalstem cell; e) an endometrial regenerative cell; f) a peripheral bloodderived mesenchymal stem cell; g) a cord blood derived mesenchymal stemcell; h) a placental derived mesenchymal stem cell; i) a Wharton's Jellyderived mesenchymal stem cell; k) a menstrual blood derived mesenchymalstem cell; and l) an endometrial derived mesenchymal stem cell. Furtherembodiments encompass methods wherein ERCs are cultured in a DMEM F12media in approximately 10% fetal calf serum for a period of 1-100 hours.

BRIEF DESCRIPTION OF THE DRAWINGS

It will be appreciated that the drawings are not necessarily to scale,with emphasis instead being placed on illustrating the various aspectsand features of embodiments of the invention, in which:

FIG. 1 is a bar graph showing various cell cultures ability to inhibitMLR

FIG. 2 is a conceptual model of ERX-EX Enhancing Engraftment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Exosomes are nanoparticles (40-100 nm) in size that possess highlydefined homogeneous characteristics [1]. Originally thought to be aby-product of cell protein turnover [2], these particles are becomingappreciated as a critical means of intracellular communication in areasranging from neurotransmission [3], to immune modulation [2], toinfectious disease [4]. Compared with other secreted vesicles, exosomeshave much better defined biophysical and biochemical properties,specifically, they have a diameter of 40-100 nm (with a density insucrose of 1.13-1.19 g/ml, and can be sedimented at 100,000 g [1]. Theirmembranes are enriched in cholesterol, sphingomyelin and ceramide, andare known to contain lipid rafts. Exosomes were originally discovered asa means of exportation of the transferin receptor during sheepreticulocyte maturation [5]. In recent years an explosion of interest inexosomes has occurred, with a wide variety of cells being reported tosecrete these nanoparticles ranging from T cells [6, 7], B cells [8, 9],dendritic cells [10, 11], tumor cells [12, 13], neurons [14, 15],oligodendrocytes [16], and placental cells [17]. It is believed thatexosomes play fundamental role in immune escape of the “fetal allograft”[18]. Endometrial regenerative cells (ERC) are believed to be precursorsof MSC that development into the maternal portion of the placenta. Giventhe high angiogenic activity of ERC, as well as their ability to inducetherapeutic effects in xenogeneic immune competent models [19], oneembodiment of the invention is the utilization of ERC exosomes as anon-cellular method of inducing immune modulatory effects that arepresent when ERC are administered therapeutically. In anotherembodiment, exosomes from other stem cells may be utilized forimmunotherapeutic purposes.

Immunological functions of exosomes were first identified in B cells[20], through studies demonstrating that these cells contain a lateendocytic compartment, called MIIC (major histocompatibility complex MHCclass II-enriched compartment), that harbors newly synthesized MHC classII molecules in transit to the plasma membrane. It was found that theMIIC compartment would fuse with the plasma membrane, but instead of theMHC II molecules becoming membrane bound, some would be found in thesoluble fraction. These particles, which the investigators termed“exosomes” in reference to original work on reticulocytes [5], weredemonstrated to possess a distinct surface composition as compared tothe plasma membrane. Interestingly, in the exosomes, a highconcentration of MHC I and II, as well as antigen were found. In 2004our group filed Canadian Patent #2453198 entitled “QUANTIFICATION ANDGENERATION OF IMMUNE SUPPRESSIVE EXOSOMES” . To our knowledge these werethe first data demonstrating that in certain contexts, exosomes maysuppress the immune system. These data, which were subsequentlypublished, demonstrated that exosomes from prostate cancer patientssuppress T cell activation in an MHC I and Fas ligand dependent manner[21]. In one embodiment of the invention, methodologies used forpurification of immune suppressive exosomes from tumor cells,incorporated by reference, are applied to conditioned media of stemcells, specifically of mesenchymal stem cells, and more specifically ofendometrial regenerative cells, in order to isolate, concentrate andtherapeutically administer exosomes derived from stem cells for immunemodulatory purposes.

We have previously published that immature dendritic cells promoteinduction of tolerance [22], and that administration of this“tolerogenic vaccine” is capable of suppressing autoimmunity in an invivo manner [23]. Given the notion that mature dendritic cell exosomesare immune stimulatory [24, 25], it was logical to investigate whetherexosomes generated from “tolerogenic” dendritic cells may prevent immuneactivation. Indeed Ruffner et al. demonstrated that dendritic cellstreated with IL-10 to block maturation secreted exosomes that inhibitedimmune response in an antigen-specific manner in the delayed typehypersensitivity system [26]. Furthermore, they demonstrated that theimmune inhibiting effect of the IL-10-treated exosome required presenceof CD80 and CD86 on the exosome. Yang et al used donor-strain derivedexosomes from immature dendritic cells to enhance allograft survival ina F334>Wistar intestinal allotransplantation model [27]. The researchersdemonstrated that as little as 20 ug of donor (but not recipient)derived exosomes was capable of causing a more than double increase ingraft survival. Similar prolongation of graft survival using donorimmature dendritic cell isolated exosomes was observed in a cardiacallograft model by another group [28]. Kim et al demonstrated thatexosomes mediating effects of tolerogenic DC were on average 75 nm insize [29] and depended on FasL for mediation of suppressive effects on Tcells using KLH recall response as an output assay. Exosome productionfrom tolerogenic dendritic cells may be labeled by some as“artifactual”, therefore, let us examine the relevance of exosomes innaturally-occurring examples of immunological tolerance. In oneembodiment of the invention, techniques used to enhance immunesuppressive activities of exosomes secreted by other cells are appliedto stem cells, mesenchymal stem cells and endometrial regenerative cellsin order to augment immune suppressive activities. For example, ERC maybe treated with compounds that inhibit inflammatory signals, such asIL-10, in order to generate populations of ERC that produce exosomeswith enhanced immune modulatory activities. Conversely, in other aspectsof the invention, exosomes may be purified from ERC that are growingunder standard culture conditions.

The term “fetal allograft” has been often used to refer to the abilityof the genetically mismatched fetus to survive within the mother.Although the fetal maternal barrier was originally believed to act as abarrier to trans-placental traffic, this was later found to beerroneous. Murine embryo transfer experiments utilizing wild-typeembryos transferred into pseudopregnant LacZ mothers demonstratedextensive maternal cell infiltration, persisting into adulthood [30].Conversely fetal cells have been demonstrated to enter maternalcirculation and play both therapeutic [31] and pathological roles [32]depending on context. It has become apparent that during pregnancy,local and systemic immune deviation occurs [33], and that failure toinduce this “natural immune modulation” is associated with recurrentspontaneous abortions [34, 35]. It appears that exosome production isassociated, at least in part, with reprogramming of the maternal immunesystem to accommodate the allogeneic fetus. In 2005, Frängsmyr et al.reported that fetal syncytiotrophoblast cells express intracellular Fasligand (FasL), which is secreted as exosomal particles into systemiccirculation. They also found similar FasL expressing exosomes to begenerated by cultured trophoblast cells [36]. As mentioned above in theexamples of cancer-derived exosomes, and tolerogenic dendritic cellderived exosomes, FasL expression on these particles is associated withkilling of activated T cells. Therefore, it may be conceptually possiblethat in physiological situations in which tolerogenesis is required,exosomes bearing antigen on MHC I/II, with or without costimulation,transmit a signal to the T cells that activate themantigen-specifically. The activated T cell then receives a “deathsignal” from the FasL, causing specific killing of the T cell clonesthat pose a threat to the exosome-producing entity. A functionalassociation between FasL expression, exosome concentration, andsuppression of T cell activity as assessed by TCR-zeta chain activitywas demonstrated in Doug Taylor's group. Furthermore, they observed thatpreterm deliveries, which are associated with higher degree ofmaternal-antifetal immunity are associated with lower concentrations ofFasL expressing exosomes [37]. Pregnancy-associated exosomes appear topossess multiple means of modulating T cell responses. For example, thesame group demonstrated that the “co-inhibitory” molecule PD1 ligand, isalso expressed on pregnancy derived exosomes in circulation and that theinhibition of T cell activity was occurring not only at the CD4 levelbut more profoundly on CD8 T cells [38]. Another group demonstrated thatpregnancy-associated exosomes, and those isolated fromsyncytiotrophoblasts express high levels of MHC class I chain-relatedproteins A and B (MICA/B) [18]. This protein specifically binds to thenatural killer activating receptor NKG2D and suppresses NK activity.Interestingly it was found that culture of peripheral blood mononuclearcells from non-pregnant women with exosomes from pregnant women resultedin downregulation of NKG2D expression, as well as suppressed NKactivity. Additionally, pregnant women had substantially lowerexpression of NKG2D compared to non-pregnant controls. The same groupsubsequently found that pregnancy-associated exosomes express a secondfamily of human NKG2D ligands, the UL-16 binding proteins (ULBP), whichinhibit not only NK cell activity, but also CD8 T cells and gamma deltaT cells [39]. The potent immune modulation associated with pregnancy hasbeen reported to inhibit clinical autoimmunity in conditions such asrheumatoid arthritis, [40] and multiple sclerosis [41]. Interestingly, astudy in the animal model of multiple sclerosis, experimental autoimmuneencephalomyelitis, demonstrated that exosomes produced during pregnancymay be responsible for the therapeutic effects on autoimmunity [42].Thus in the situation of “natural tolerance” induced by pregnancy, itappears that exosomes play a role in temporary downmodulation ofmaternal responses. The potential of tumor-derived exosomes tokill/inactivate T cells through a Fas-FasL mechanism has beendemonstrated in ovarian cancer [43], prostate cancer [21], and melanoma[7]. However, numerous other means of immune modulation have beenascribed to cancer-derived exosomes. For example, Valenti et al showedthat exosomes from melanoma and cervical cancer patients can “reprogram”monocytes into myeloid derived suppressor cells [44]. These cells playan important role in protecting tumor cells from T cell mediatedimmunity through secretion of suppressive factors such as PGE2, nitricoxide, arginase, and production of reactive oxygen intermediates [45].Another “indirect” means by which tumor exosomes contribute to immuneevasion is through the generation of T regulatory cells [46]. It wasrecently demonstrated by Whiteside's group that co-culture of tumorderived exosomes with naive T cells, under certain conditions, wouldlead to potent generation of T regulatory cells that could suppressother T cells from activation. This concept of “infectious tolerance”has been described in the area of tumor immunotherapy with littlemechanistic knowledge. Yet another mechanism of tumor exosome immunesuppression is through the production of free adenosine via the enzymeCD73, which has been demonstrated to be expressed highly ontumor-derived exosomes 12. Induction of oral tolerance appears to beassociated with generation of T regulatory/Th3 cells that are specificto food-borne antigens [47]. While clinical trials of oral tolerance inrheumatoid arthritis [48], and multiple sclerosis [49, 50], have shownsome promising results, to date, efficacy has not been able to meet thebar required by regulators for registration. By understanding biologicalmechanisms involved in induction of this innocuous form of tolerance, itmay be feasible to develop therapeuticmodalities to increase efficacy.It was demonstrated that subsequent to feeding with a nominal antigen,plasma-circulating exosomes containing MHC II and the antigen could becaptured. In vitro culture of these exosomes revealed ability toantigen-specifically suppress T cell activation [51]. Using a murineallergy model it was demonstrated that protection from allergy could betransferred via exosomes collected from mice that had been fed theallergen orally [52]. These data suggest that tolerance induction may beoccurring through the generation of tolerogenic exosomes as had beenseen in the case of pregnancy and cancer in the previous sections. Incertain embodiments of the invention, exosomes from stem cells arepurified based on expression of certain markers that have beenassociated with naturally-occurring immune suppression induced byexosomes secreted by non-stem cells. In one embodiment, exosomes aregenerated in a means that causes preferential production of CD73expressing exosomes. Specifically, ERC are cultured under conditionsoptimized for production of CD73 expressing exosomes by variation ofculture conditions. In one specific embodiment, 10 ng/ml of IL-10 isadded to ERC in tissue culture. Culture of ERC has been described in thepaper Meng et al [53], and incorporated by reference. Specific cultureconditions and clinical use of ERC has been previously described inconditions such as congestive heart failure 54 and spinal cord injury[55]. Additionally, other cells may be used as a source of stem cellscapable of producing exosomes. Cord blood cells useful for therapeuticapplications have been described by us and are incorporated by reference[56].

Mesenchymal stem cells (MSC) are a family to which the ERC belong to. Ithas been reported that MSC express numerous immunemodulatory/suppressive properties. For example, it has been demonstratedthat MSC are therapeutically useful in clinical trials of immune-basedconditions such as graft versus host disease [57], systemic lupuserythematosus [58], multiple sclerosis [59], and rheumatoid arthritis[60]. While it has previously been demonstrated that MSC-secretedexosomes are angiogenic and possess therapeutic activity in animalinfarct models [61], the current invention is distinct from prior usesin that exosomes are utilized to elicit immune modulation. Thepossibility that MSC-derived exosomes are immune modulatory bring aboutseveral drug development options. For exsomes, exosomes have beenengineered to act as vectors for siRNA, unfortunately, to date onlydendritic cell exosomes have been used for this purpose [62]. Given thatdendritic cells are inherently immunogenic, and difficult to expand ingreat quantities due to their terminal nature, the current inventionovercomes this by providing a source of exosomes that is capable ofgeneration in large numbers.

In one embodiment of the invention, exosomes are generated from ERC thatare genetically compatible with ERC administered for the purpose of celltherapy. In one specific embodiment, a master cell bank is generatedfrom one ERC donor. During the process of ERC generation, exosomes arecollected from tissue culture media and concentrated using methods knownin the art. Specific methodologies include ultracentrifugation, HPLC,adherence to substrate based on affinity, or filtration based on sizeexclusion. Exosomes collected are administered systemically to patientsreceiving ERC therapeutically in order to enhance engraftment of ERC. Inother embodiments, ERC derived exosomes are used either as amonotherapy, or a combination therapy with other immune modulatoryinterventions in order to augment immune modulatory activities of saidtherapy.

EXAMPLE 1 ERC Exosomes Inhibit MLR and Augment ERC Ability to InhibitMLR

Exosome Purification. Exosomes were prepared from the cell culturesupernatant of day 4 ERC cultures by differential centrifugation.Briefly, recovered culture supernatant was subjected to three successivecentrifugations at 300 g (5 min), 1,200 g (20 min), and 10,000 g (30min) to eliminate cells and debris, followed by centrifugation for 1 hat 100,000 g. To remove excess serum proteins, the exosome pellet waswashed with a large volume of PBS, centrifuged at 100,000 g for 1 h, andfinally resuspended in 120 ul of PBS for further studies. The exosomeswere quantified by a micro Bradford protein assay (Bio-Rad). Each batchwas standardized by protein content, Fetal calf serum exosomes wereprepared using the same method.

Tissue Culture Peripheral blood mononuclear cells (PBMC) were isolatedfrom 5 ml of blood by Ficoll density gradient (Sigman-Aldrich) utilizingtwo HLA-incompatible donors. Cells were washed twice in phosphatebuffered saline (PBS) and plated in round-bottom, 96-well plates (Nunc).In each well, 500,000 PBMC from each donor were added to a total volumeof 200 uL in RPMI media containing 10% fetal calf serum (LifeTechnologies). In all cultures the media was centrifuged for 3 h at100,000 g to deplete of exosomes. Additionally, exosomes and/or ERC wereadded as described in the FIG. 1. On day 4, 1 uCi of [3H]thymidine wasadded to each well 16 h before harvest. Radioactive labeling ofproliferating T cells was measured on a microplate beta counter(Wallac). Data in FIG. 1 demonstrate that adding of 200×103 ERC to MLRinhibited T cell proliferation by 24% p<0.05 compared to control.Interestingly, addition of 1-2 ps of purified ERC exosomes (ERC ex)inhibited MLR significantly better. Much more importantly, adding to MLRcultures 100×103 ERC with 1-2 ps ERC ex significantly enhance immuneinhibition.

EXAMPLE 2 ERC Exosomes Enhance In vivo Engraftment of ERC in ImmuneCompetent BALB/c Mice

The previous experiments suggest that addition of ERC-Exosomes to amixed lymphocyte reaction (MLR) enhances ability of the ERC cell todecrease ongoing immune response in vitro. Accordingly, we sought todetermine whether co- administration of exosomes may enhance engraftmentof ERC. As seen in Table 1, administration of 40 and 80 micrograms ofERC-Exosomes per mouse was sufficient to significantly enhance ERCengraftment.

TABLE 1 Adminstation of ERC-EX Increases Human ERC Engraftment in InnumeCompetent BALB/c Mice Treatment 1 hr 7 days 14 days 30 days ERC*28(±5)^(#)  2(±1) 0(±1) 0(±0) ERC + 10 ug 32(±7)  5(±4) 4(±3) 3(±3)ERC-EX ERC + 20 ug 25(±9) 18(±4) 6(±5) 4(±1) ERC-EX ERC + 40 ug 26(±5)22(±1) 19(±2)  17(±3)  ERC-EX ERC + 80 ug 33(±3) 24(±4) 25(±4)  19(±5) ERC-EX *ERC were administered into the gastrocnemius muscle at aconcentration of 100,000 cells. ^(#)Detection of human cells wasperformed using mouse anti-human CD44 Thermo Scientific, Clone 156-3C11)and secondary antibody, anti-mouse IgG2a (Lab Vision, NC-1390),immunoflourescence of Alexa was detected. Numbers represent cells permicroscope viewing field at 200X magnification in a total of 5 slides.Mice were sacrificed at the indicated days.

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What is claimed is:
 1. A method of inducing immune modulation in amammal comprising the steps of: a) extracting a stem cell population; b)culturing said stem cell population for a sufficient time point, underconditions permissible for exosome production; c) collecting exosomesgenerated by said stem cells; d) concentrating said exosomes; and e)administering said exosomes to said mammal.
 2. The method of claim 1,wherein said stem cell comprises a cell selected from: a) a progenitorcell; b) a pluripotent stem cell; c) an induced pluripotent stem cell;d) a hematopoietic stem cell; e) a very small embryonic like stem cell;f) a mesenchymal stem cell; g) an endometrial regenerative cell (ERC);h) a progenitor cell; and i) a monocyte.
 3. The method of claim 1,wherein said stem cells are induced to produce an increased amount ofexosomes.
 4. The method of claim 3, wherein said induction of exosomesfrom said stem cells is achieved by treatment of said stem cells withcytokines
 5. The method of claim 1, wherein said exosomes areconcentrated by a means selected from: a) ultracentrifugation; b) columnchromatography; c) size exclusion; d) filtration through a devicecontaining an affinity matrix selective towards exosomes.
 6. The methodof claim 1, wherein said exosomes generated from said stem cells areused to inhibit inflammation in an injured tissue.
 7. The method ofclaim 1, wherein said exosomes are transfected with a genetic materialso as to allow delivery of said genetic material to an immune cell. 8.The method of claim 1, wherein said cells producing said exosomes aretransferred with a genetic material so as to allow delivery of saidgenetic material to an immune cell.
 9. A method of treating anautoimmune condition through administration of a population of stem cellexosomes capable of suppressing a biological pathway associated with animmune pathway associated with said autoimmune condition.
 10. The methodof claim 9, wherein said autoimmune condition is selected from a groupcomprising of: a) diabetes; b) multiple sclerosis; c) rheumatoidarthritis; d) Hashimoto's thyroiditis; e) graft rejection; and f) graftversus host disease.
 11. A method of treating an autoimmune conditioncomprising incorporating one or more autoantigens into said exosomesgenerated from said stem cells, with incorporation of said autoantigenbeing accomplished by introduction into said stem cell or introductioninto said exosome generated by said stem cell and administering saidexosomes into a patient in need thereof.
 12. A method of treating anautoimmune condition in a mammal comprising administering exosomesderived from stem cells that have been transfected one or moreautoantigens representing said autoimmune condition.
 13. A method oftreating an autoimmune condition comprising of: a) obtaining amesenchymal stem cell; b) introducing into said mesenchymal stem cell anantigen, in a manner such that said antigen is introduced into saidmesenchymal stem cell in a manner so that said antigen is incorporatedby said mesenchymal stem cell such that said antigen enters the exosomesthat are released by said mesenchymal stem cell; c) purifying saidantigen bearing exosomes; and d) administering said antigen expressingexosomes into a patient in need of therapy.
 14. The method of claim 13,wherein said mesenchymal stem cell is selected from a group ofmesenchymal stem cells selected from a group comprising of a) a bonemarrow mesenchymal stem cell; b) an adipose derived mesenchymal stemcell; c) a dental pulp derived mesenchymal stem cell; d) a fallopiantube derived mesenchymal stem cell; e) an endometrial regenerative cell(ERC); f) a peripheral blood derived mesenchymal stem cell; g) a cordblood derived mesenchymal stem cell; h) a placental derived mesenchymalstem cell; i) a Wharton's Jelly derived mesenchymal stem cell; k) amenstrual blood derived mesenchymal stem cell; and 1) an endometrialderived mesenchymal stem cell.
 15. The method of claim 14 wherein ERCare cultured in a DMEM F12 media in approximately 10% fetal calf serumfor a period of 1-100 hours.
 16. The method of claim 13, wherein saidexosomes are concentrated by a means selected from: a)ultracentrifugation; b) column chromatography; c) size exclusion; d)filtration through a device containing an affinity matrix selectivetowards exosomes.
 17. The method of claim 13, wherein said antigen isincorporated into said exosome-producing mesenchymal stem cell through aseries of procedures selected from: a) transfection with the geneencoding said antigen; b) transfection with said antigenic protein; andc) transfection with said antigenic peptide.
 18. The method of claim 13,wherein said antigen is loaded onto said mesenchymal stem cell producedexosomes.
 19. The method of claim 18, wherein said loading of saidantigen is accomplished through chemical means.